Physico-Chemical Factors and Bacteria in Fish Ponds

Transcription

1 Physico-Chemical Factors and Bacteria in Fish Ponds X. Jun, F. Xiuzheng and Y. Tongbing Abstract Analyses of pond water and mud samples show that nitrifying (including ammonifying, nitrite, nitro and denitrifying ) are in general closely correlated with various physico-chemical factors; ammonifying are mainly correlated with dissolved oxygen; denitrifying are inversely correlated with phosphorus; nitrite are closely correlated with nitrites, nitro are inversely correlated with ammoniac nitrogen. The nitrifying are more closely correlated with heterotrophic. Nitro are inversely correlated with anaerobic heterotrophic. The correlation is quite weak between all the nitrite which indicates that the nitrite have a controlling and regulating function in water quality and there is no interdependence as each plays a role of its own. The paper also discusses how the superficial soil (pond mud down to 3.5 cm deep) and different layers of the mud affect the biomass of. The study shows that the top superficial layer (down to 1.5 cm deep) is the major area for decomposing and converting organic matter. Introduction The nitrogen cycling process in a pond is mainly carried out by ammonifying, nitro, nitrifying and denitrifying (generally called nitrite ). These nitrifying play a vital role in water quality control. Water quality is an important indicator in appraising the eutrophic situation, primary productivity and fish yield potential. The relationship between and the water environment has received the attention of researchers, but the studies undertaken have been mostly limited to the relationship between the aerobic heterotrophic or total and the water environment (Guo et al. 1988; Fang et al. 1989; Zhang et al. 1989; Liu et al. 1992(a)). There is not much information on the relationship between anaerobic and major physico-chemical factors, particularly the nitrifying affecting water quality. Studies were undertaken to assess the relationship between and nitrogen in fishponds. The results of these studies are presented in this paper. These studies also analyzed the topsoil of the pond mud (Fang et al. 1993). Other studies have been made to find out the activation of the pond mud. The results showed that the superficial pond mud down to 1.5 cm deep is where most of the decomposition and conversion of nitrogenous organic matter takes place. Use of modern microbiology to increase the activation of pond mud and improve water quality is a new approach to reducing outbreaks of diseases and sustaining the development of aquaculture. Materials and Methods The study was undertaken in an intensive polyculture pond of 0.48 ha with a water depth of 2.5 m, situated in No. 1 Fishery Team, Helei Village in Wuxi, China. The pond was stocked with black carp (Mylopharyngodon piceus), grass carp (Ctenopharyngodon idella), Wuchang fish (Megalobrama amblycephala), common carp (Cyprinus carpio), silver carp (Hypophthalmichthys molitrix), bighead carp (Aristichthys nobilis) and crucian carp (Carassius carassius). They were fed from March to October with grass (rye grass, land grass and cabbage), shellfish (snails) and commercial feeds (wheat, rice dregs, bean cakes and pellet concentrates). Soil and water sampling was undertaken between April and October. The samples were collected at three spots in the pond and mixed together. The mud was collected in cylindrical glass bottles (5 cm in diameter) at two levels: cm depth (layer 1) and cm depth (layer 2). Samples of 50 g each collected from the three sites were mixed and diluted in 450 ml of germfree distilled water for analysis. 16 Naga, The ICLARM Quarterly (Vol. 23, No. 4) October-December 2000

2 Table 1. Bacteria biomass in the first layer of pond mud. Date *Aerobic *Anaerobic Aerobic Anaerobic Ammonifying Nitro Nitrifying Denitrifying x10 5 x10 5 * x10 5 x10 5 x10 5 x10 x10 x10 5 (ind/ml) (ind/ml) (ind/ml) (ind/ml) (ind/ml) (ind/ml) (ind/ml) (ind/ml) 4/ / / / / / / / / / / / / a q u a b y t e *indicates the in the water body, the rest from the first layer of the mud. The plate method was used for the determination of aerobic and anaerobic heterotrophic and MPN (Most Probable Numbers) method was used for ammonifying, nitrifying, nitro and denitrifying. A CO 2 incubator was used for the culture of anaerobic and denitrifying and a common incubator for ammonifying. The total nitrogen and ammoniac nitrogen were determined by colorimetric analysis; the nitrate nitrogen was determined by the phenoldi-acid method; nitronitrogen by the a-naphthylamine-p- Aminobenzene sulfonic acid anhydrous colorimetric method; total phosphorus and dissolved phosphates were determined by the molybdenum blue colorimetric method and the dissolved oxygen content was determined by a YS 157 oxygen meter. Results Aerobic heterotrophic in the pond water fluctuated between x 10 5 ind/ml, the anaerobic heterotrophic fluctuated between x 10 5 ind/ml, which is slightly higher than the former (mean value is about 2 times greater) (Table 1). The result seems to indicate that even if the dissolved oxygen is sufficient in the water, apart from the aerobic, there might be also anaerobic heterotrophic. In the reduced oxygen condition, the anaerobic maintain their existence and balance through denitrifying and denitrification (Fang et al. 1993; Molongoski and Clug 1980). Bacteria Biomass in Pond Mud The aerobic heterotrophic in the first layer of pond soil fluctuated between x 10 5 ind/ml and the anaerobic heterotrophic between x 10 5 ind/ml. Ammonifying fluctuated between x10 5 ind/ml, denitrifying between x 10 5 ind/ml; the nitrifying between ind/ml; and the nitro between ind/ml (Table 1). Table 2 shows that the aerobic heterotrophic in the second layer of pond soil fluctuated between x 10 5 ind/ml, anaerobic heterotrophic x 10 5 ind/ml. Ammonifying fluctuated between x 10 5 ind/ml, denitrifying between x 10 4 ind/ml; nitro between ind/ml, and nitrifying between 0-45 ind/ml. Discussion Decomposition of Nitrogenous Organic Matter Pond soil is an important component in pond ecology and can absorb nitrogen and phosphorus and some undecomposed organic matter that has settled on the bottom. The nutritional elements from the soil are further released into the water body. Sun Yao et al. (1997) reported that the contact layer between pond mud surface and water is the major source of nutrition. The organic nitrogen is decomposed to NH 4+ -N which adheres to the surface of the mud before being released in the water where it continuously rises to the Naga, The ICLARM Quarterly (Vol. 23, No. 4) October-December

3 surface of the water and escapes to the air (Mei et al. 1995; Blackburn and Henriksen. 1985). Several scholars have agreed that the nutrients NH 4+ -N and PO 43 -P are released only from mud 0-2 cm thick (Mei et al. 1995; Blackburn and Henriksen 1985; Maeda et al. 1987). Mei et al. (1995) reported that the decomposition depth of organic carbon reaches 4 cm, the organic nitrogen can reach 4-6 cm, but major organic content is within 0-2 cm. Carignan and Flett (1981) reported that sulphuret within only 2 cm can be oxygenation-reduced before settling down. It is considered that nitrogen is first converted to ammonia-nitrogen by the ammonifying during the decomposition of nitrogenous organic matters. Then, ammonianitrogen is converted to nitrite by nitro. Then, nitrite is converted to nitrate by nitrifying. Finally, nitrate is converted to nitrite, N 2 and N 2 O by denitrifying. There is a widespread distribution of ammonifying and denitrifying, but it is concentrated in the pond mud. The nitrifying and nitro are only available on the superficial mud. The present studies also determined the quantity of the. t-tests show that nitrite is different in biomass with the variation of the pond mud stratification, the contact between water and mud has a higher quantity of compared to the upper water levels and deeper mud. In general, the decomposition of the nitrogenous organic matters is mainly at the water-mud surface, which is also a key area of energy flow. Nitrifying Bacteria and Physico-chemical Factors There are many studies on the relationship between aerobic heterotrophic and water quality (Guo et al. 1988; Fang et al. 1989; Liu et al. 1992(a); Liu et al. 1992(b)). However, information on the relationship between nitrite and major physicochemical factors is limited. Table 3 indicates that ammonifying have high correlation with dissolved oxygen content (r=0.693, p<0.05). The major role of ammonifying is to break down nitrogenous organic matter to ammoniac nitrogen. Increase in dissolved oxygen content accelerates the decomposition process of organic matters. Denitrifying have an inverse correlation with phosphorus (r=-0.648, p<0.05). Denitrifying convert the nitrate into nitrite, N 2 and N 2 O. The increase of phosphorus content inhibits the activity of denitrifying and increases the nitrite in the pond. Nitro have inverse correlation with ammoniac nitrogen (r=-0.694, p<0.05). The main role of nitro is to break down ammoniac nitrogen into nitrite. Frequent feeding, aeration and fish excreta increase the level of ammoniac nitrogen. Thus, the enhancement of ammoniac nitrogen content inhibits the activity of nitro. Nitrifying have direct correlation with nitrite (r=0.638, p<0.05). The nitrifying convert the nitrite to nitrate. In general, the nitrite content is the lowest among the content of ammonia nitrogen, nitrite and nitrate in pond. Thus, the amount of nitrifying is the lowest among the ammonifying, nitro, nitrifying and denitrifying. Theoretically speaking, the aerobic should have a direct correlation with dissolved oxygen content and an inverse correlation Table 2. Bacteria biomass in the second layer of pond mud. Date Aerobic Anaerobic Ammonifying Nitro Nitrifying Denitrifying x10 5 x10 5 x10 5 x10 5 x10 5 x10 (ind/ml) (ind/ml) (ind/ml) (ind/ml) (ind/ml) (ind/ml) 4/ / / / / / / / / / / / / Naga, The ICLARM Quarterly (Vol. 23, No. 4) October-December 2000

4 Table 3. Correlation between (i) different ; and (ii) and major physio-chemical factors in the first layer of pond soil. Variables Aerobic Anaerobic Ammonifying Denitrifying Nitro Nitrifying r p r p r p r p r p r p Anaerobic a q u a b y t e Ammonifying Denitrifying Nitro Nitrifying Dissolved oxygen Chlorophyll-a Available phosphorus Ammoniac nitrogen Nitrates Nitrites r = Correlation p = Probability-value Table 4. t-test on from the two layers of soil. Name Soil layer Times of Standard Degree of P value determination deviation freedom Ammonifying Denitritying Nitro Nitrifying Aerobic Anaerobic All, except nitro, in the first layer of pond soil have a significant difference (p<0.01) from those in the second layer of the soil. with anaerobic. In fact aerobic are directly proportional to anaerobic (r=0.929, p=0.000) and in inverse proportion to dissolved oxygen content (r=-0.665, p=0.036). A likely explanation for this is that both aerobic and anaerobic have a double function in relation to changes in dissolved oxygen content. Because of the low oxygen content in the contact surface between the water and the soil, the heterotrophic are more suitable for anaerobic conditions. The nitrifying have weak correlation between themselves (r<0.60, p>0.05). The contact surface between the water and the soil is dominated by the heterotrophic. The nitrifying are strongly correlated with physio-chemical factors, indicating that they have an important role in the management of water quality. Naga, The ICLARM Quarterly (Vol. 23, No. 4) October-December

5 References Molongoski, J.J. and M.T. Clug Anaerobic metabolism of particulate organic matter in the sediment of a hypereutrophic lake. Freshwater. Biol. 10: Carignan, R. and R.J. Flett Postdepositional mobility of phosphorus in lake sediment. Limnol. Oceanogr. 36(2): Lei Yanzhi and Li Yonghan The studies on the water quality, hydrochemistry and primary productivity in Helei High-yield Fish Pond, Wuxi. Fishery Journal 7(3): Blackburn, T.H. and K. Henriksen Nitrogen cycling in different types of sediments from Danish waters. Limnol. Oceanogr. 28(3): H. Maeda Changes in the qualities of water and bottom sediment with the development of anoxic layer in a stratified lake. Nippon Sojima 53(7): Guo Xianzhen; Fang Yingxue and Wang Jikun The preliminary studies on the types in the fish ponds applied with four kinds of animal manure and the effects upon ecosystem and yield. J. Chinese Acad. Fish. Sci. 1(1): Fang Xiuzheng; Guo Xianzhen and Wang Jikun The preliminary studies on the heterotrophic in high-yield fish ponds. Fishery Journal 13(2): Zhang Zhongyang and Tang Yujun Pond fish culture in China. Beijing Science Publishing House. p Liu Guocai; Bao Wenzhong and Liu Zhenqi. 1992(a). The growth and seasonal changes of biomass in fishponds. Fishery Journal 16(1): Liu Guocai; Bao Wenzhong and Liu Zhenqi. 1992(b). Preliminary studies on the in pond mud. J. Fish. Biology. 16(3): Fang Xiuzheng; Guo Xianzhen and Yu Tongbing The in nitrogen cycling and mud activation in the pond mud. Fishery Journal. 17(2): Shi Zhenfeng; Zhu Xuebao and Mei Zhiping The preliminary studies on the sedimentation of the organic matters in fish pond. The Studies of the Ecosystem in the Chinese Fish Pond. Shanghai Science and Technology Press. p (Editor: Zhu Xuebao and Shi Zhenfeng) Sun Yao and He Zhaoyang Shrimp pond settlement the quantity of nutrients dispersion and seasonal changes between water and mud contacting surfaces. Mar. Fish. Res. 18(1): Mei Zhiping; Shi Zhenfeng and Zhu Xuebao The studies on the nutritional content and the release of the fish pond mud, p The Studies of the Ecosystem in the Chinese Fish Pond. Shanghai Science and Technology Press. (Editor: Zhu Xuebao and Shi Zhenfeng) X. Jun, F. Xiuzheng and Y. Tongbing are from the Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, Wuxi, , China. 20 Naga, The ICLARM Quarterly (Vol. 23, No. 4) October-December 2000